Improper burial and storage conditions significantly impact the degradation process of mummies. Factors such as pressure, fluctuations in humidity and temperature, and exposure to light can accelerate this degradation. This study focuses on understanding the degradation mechanism of a mummy from the Late Period, currently stored in the excavation stores at Saqqara, Giza, Egypt. Various techniques including temperature and humidity monitoring, light intensity measurement, internal water content analysis, digital microscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy (FESEM-EDX), X-ray radiography, internal endoscopy, Fourier-transform infrared spectroscopy (FTIR), and isolation and identification of fungi were employed to investigate the mummy's condition.The study found that the soil's mechanical stress caused bone fractures in the mummy's body. Increased humidity led to the dissolution of natron salt, which penetrated the body and surface, resulting in decay of soft tissue and bone. Various microscopes revealed cracks, insect holes, and other damage. Internal endoscopy confirmed body removal and decay. X-ray radiography showed the brain had been removed without resin filling the space. FTIR analysis identified the presence of natron salt, bitumen, beeswax, Arabic gum, and plant oil in the mummification process. Additionally, it showed the chemical stability changes in the mummy components. Fungi such as Penicillium implicatum, Aspergillus flavus, and Trichoderma sp. were also identified.